-INSTALLATION GUIDELINES-

1. Care during installation
   Care should be be taken to prevent damage to the tubing during the backfilling operation.   Avoid dropping large soil clods or rocks directly on the tubing.  Heavy loads of all types should be avoided until the soil around the installation area is properly settled.

2. Bedding
   Tubing should be bedded in gravel.  However, selected soil backfill material such as crushed stone or compacted soil may also be used with satisfactory results.  The bedding material should be placed around the tubing to a depth at least 2'' over the top of the tubing.  When selected soil bedding material from the trench excavation is used, choose small loose particles of soil that will flow around the tubing and minimize soil settling. Avoid large rocks that may damage the tubing or large clods of soil that cause voids and subsequent excessive settling.

3. Depth of cover
   If vehicular traffic is expected over tubing, there should be a minimum of 12'' of cover over tubing if gravel bedding material is used and 24'' of cover if selected soil bedding material is used.  Typical recommended gravel materials would be pea gravel, GA stone or pit run course sand and gravel mixes.

4. Proper grade
   The grade, or fall, on which tubing is laid is important in that reversals in grade will reduce the effectiveness of the system.  Best drainage results are achieved with a continuous downhill fall, or grade, over the entire length of the drain line.  A fall of 0.2 inches per 10 feet of length is generally considered adequate.  Greater fall will promote more rapid drainage.

5. Proper selection of Baughman Tile materials
   Choose your materials according to application.  If absorption and drainage are required, perforated tubing should be used.  If tubing serves only to move water away from area (such as downspout run-offs, etc), non-perforated tubing is best because it will not dissipate water into the surrounding area.  Non-perforated tubing should also be used if the line runs close to trees where root penetration may be a problem.  If the soil being drained is sandy and silty, then either Poly-Drain® protective wrap or gravel should be used to prevent the soils from entering and blocking the drainage line.

TRENCH DIMENSIONS

TYPICAL BACKFILL ENVELOPE

The backfill envelope can be considered to have specific zones, each having a specific purpose.

• Bedding provides a uniform base to ensure that grade is maintained and that loads can be distributed into the foundation
• Haunching extends from the bedding to the pipe springline, or midpoint.  This section of the backfill performs primarily by resisting applied loads.
• Initial backfill, situated above the springline to a point at least 6" (0.15m) above the crown, supports loads on either side of the pipe.
• Final backfill helps distribute surface-applied loads.  The height of the initial and final backfill areas should be at least 1' (0.3m) over the pipe crown in installations involving maximum loads of AASHTO H-20 or HS-25.

MINIMUM COVER REQUIREMENTS FOR CORRUGATED POLYETHYLENE PIPE

Based on Class III Backfill Compacted to 90% Standard Proctor Density and AASHTO H-20 Load

Note: Class III materials are gravel/sand/silt/clay mixtures with limited fines.  (Refer also to the CPPA technical booklet Structural Design Method for Corrugated Polyethylene Pipe.) Minimum covers presented here were calculated based on at least 6" (0.15m) of structural backfill material over the pipe crown with an additional layer of compacted native soil for a total cover as shown.  In shallow, high traffic installation, especially where pavement is involved, it may be best to use a good-quality compacted material to grade to prevent surface settlement and rutting.

MAXIMUM COVER HEIGHTS FOR CORRUGATED POLYETHYLENE PIPE

feet (meters)

Backfill Condition

Pipe Inside Diameter, ID
in (mm)